Aproveitamento do soro do queijo "coalho" para produção e aplicação da β-galactosidase

Abstract

The present study aimed to produce the enzyme β-galactosidase (β-gal) using “coalho” cheese whey as biotechnological substrate by yeasts of the genus Kluyveromyces and to evaluate processing strategies that enable its application in the food industry. In the first stage of this study, the co-production of β-gal and ethanol by submerged fermentation in shake flasks and bioreactors using different carbon/nitrogen C:N rations (1.5:1 and 2.5: 1). The best efficiency was obtained with Kluyveromyces lactis NRRL Y-8279, which produced 21.09 ± 0.69 U / mL β-gal and 7.10 ± 0.09 g / L ethanol in 16 hours of cultivation. Based on the initial results, the βgal purification conditions in fixed bed chromatography were evaluated using experimental design 22 . The pH and ionic strength parameters were evaluated considering the purification factor, without prejudice to yield. Higher levels of both parameters in the study increased the β-gal purification factor (PF) to 2.00, with greater influence of ionic strength on the PF response. The partially purified enzyme was submitted to electrophoresis, which presented a band with molecular mass in the range between 66 and 140 kDa, configuring the enzyme of interest. In the last stage of the study, lactose hydrolysis conditions were observed in the curd cheese whey with the immobilized form of β-gal in 1% (w/v) sodium alginate. The immobilization efficiency reached 66% and high recovered activity was achieved. In addition, the immobilized form of the enzyme presented higher stability to pH and temperature changes and a lactose conversion (46%) without major aesthetic differences when compared to the crude enzyme extract (53%). For the gastrointestinal simulations, around 40% of the enzymatic activity was preserved after 2 hours of exposure to simulated gastrointestinal environments. Overall, the results described here are promising for the industrial applications of βgalactosidase from K. lactis.